A cricket’s constant chirping may seem a bit ballsy, but just wait until you hear about their testicles. For at least one species of cricket, the tuberous bushcricket (Platycleis affinis), the testicles take up 14 percent of the insect’s body mass!

To put this into perspective, a man with the same proportions would have to carry testicles weighing as much as five bags of sugar each.

The discovery, made by a team led by Karim Vahed, was published in Biology Letters today. Vahed said in a press release that he was surprised by the finding:

“We couldn’t believe the size of these organs, they seemed to fill the entire abdomen. We are also interested in the reason why they are so large. An almost universal evolutionary rule appears to be that such variation in relative testes size is linked to female mating behaviour; testes tend to be larger in species where females are more promiscuous, as has been demonstrated in various species in fish, birds, insects and mammals.”

Traditionally scientists have seen that promiscuous partners lead to bigger balls through male competition. Each male wants to make more sperm than the rest so that his boys have the best chance of winning the race, either by sheer volume or through an ability to mate more often. This seems to be the case in these crickets, Vahed explained in a press release:

“It looks as though the testes may be that big simply to allow males to mate repeatedly without their sperm reserves being exhausted,” Dr Vahed said. “This strongly suggests that extra large testes in bushcrickets allow males to transfer relatively small ejaculates to a greater number of females. Males don’t put all their eggs (or rather sperm!) in one basket.”

The researchers discovered that each female bushcricket takes many mates, up to 23 in a two-month adult life. It seems this lifestyle has driven the males’ evolution of mega-testicles, giving them the stamina to keep up with these promiscuous ladies, explained The Guardian:

The theory, while speculative, has some evidence to support it. After mating with one female, tuberous bush crickets were ready to mate again within an hour, while other species with smaller testes took as long as five days to be ready.